Pedestrians are much more terrified of bicycles than cars, makes sense to put the guardrail there to protect them from vicious cyclists.

The guardrail can serve the don’t-drive-off-embankment function equally well positioned before the sidewalk. The problem is when an out-of-control car strikes the guardrail at a glancing angle, it takes a long time (by design) to grind down to a stop. This creates a bowling alley effect. The guardrail keeps the speedy car centered right on the sidewalk. Any human bowling pins are toast. Some of the most horrific traffic death videos I’ve seen involve that. Whole families wiped out.

Is that a bicycle path and a dirt running track, or is the desire path in the dirt the official bicycle route and the side road behind the guardrail is for horses or golf carts or something?

Saw an example of correct guardrail usage today, with the overgrown path that some other commenters were worried about.

(Lincoln Highway Hackensack River Bridge in Newark)

Let me tell you one thing, I would 100% rather ride on this overgrown sidewalk than on the shoulder of the 55mph highway without a shoulder. This is the official bicycle/pedestrian bridge crossing. I wasn’t sure whether the bridge path is even open or exists, but it does and there were even other people using it. (There is a second mesh fence on the embankment side, more so to protect the bushes than to stop you falling over.)

And then take a look at this other beauty today:

(Weequahic Park Drive, New Jersey)

Correct guardrail usage AND perfectly maintained path! Alas, pedestrian only, but not a problem to ride on 25mph street. Proof that putting the guardrail before the sidewalk is perfectly possible, both legally and practically. (There is a lake down the embankment. Don’t walk into the lake.)

In NYC they put parking meters on the sidewalk behind metal bollards. Note that they do not put bollards on street corners at pedestrian crossings. Even in the modern intersection redesigns with the wider sidewalk cutouts, the DOT still only ever uses collapsible plastic bollards at best, if at all. Every time I wait for a crossing light as a pedestrian in one of those brown-paint-only sidewalk cutouts at street level, I look over my shoulder to one of these parking meters up on the curb behind their bollards and awe at how much more protection a dumb piece of metal street furniture gets than the squishy me.